A team of scientists has used the NASA/ESA Hubble Space Telescope to observe a quasar accretion disc — a brightly glowing disc of matter that is slowly being sucked into its galaxy’s central black hole.

Large-Scale Structure of the Cosmos -- Stars are organised into galaxies which in turn appear to form clusters and superclusters, separated by voids.
Prior to 1989 it was commonly assumed that the superclusters were the largest structures in existence, and that they were distributed more-or-less uniformly throughout the universe in every direction.
However, in 1989, Margaret Geller and John Huchra discovered the "Great Wall", a sheet of galaxies more than 500 million light years long...

Supermassive Black Hole -- A Supermassive black hole is a black hole with a mass in the range of millions or billions solar masses.
A supermassive black hole has some interesting properties differing from his low-mass cousins:
-- The average density of a supermassive black hole can be very low, and actually can be lower than water's density. This happens because the black hole diameter increases linearly with mass, and consequently density drops much faster.
-- Strong tidal...

Redshift -- Redshift is the phenomenon that the frequency of light when observed, under certain circumstances, can be lower than the frequency of light when it was emitted at the source.
This usually occurs when the source moves away from the observer, as in the Doppler effect. More specifically, the term redshift is used for the observation that the spectrum of light emitted by distant galaxies is shifted to lower frequencies (towards the red end of the spectrum, hence the name) when...

Microquasar -- Microquasars are smaller cousins of quasars. They are named after quasars, as they have some common characteristics: strong and variable radio emission often seen as radio jets, and an accretion disk surrounding a black hole.
In quasars, the black hole is supermassive (millions of solar masses) as in microquasars, the black hole mass is a few solar masses. In microquasars, the accreted mass comes from a normal star and the accretion disk is very luminous in optical regions...

Gravitational Lens -- A gravitational lens is formed when the light from a very distant, bright object (such as a quasar) is "bent" around a massive object (such as a massive galaxy) between the bright object and the viewer. The process is known as gravitational lensing, and was one of the predictions made by Einstein's general relativity.
Description
In a gravitational lens, the gravity from the massive object bends light as a lens might. As a result, the path of the light from a...